The great autumn galactic happening
Now that we're well into early autumn and the bright light of the harvest moon is long gone, it's a fabulous time to make a date to get out in the dark skies of the countryside, that is, if you're not already living out there.
I guarantee this will be a treat you'll remember for a long time, whether by yourself or with family or friends. Bring blankets, binoculars, star charts, snacks and beverages, and be prepared to sleep in the following day. Even better, turn this into an overnight campout if you don't mind braving the October chill! It will be a great show. The clear autumn skies are more transparent because the air has much less humidity.
For the heck of it, when you settle under the autumn evening heavens, attempt to estimate how many stars you can see with your naked eye.
Traditional astronomy textbooks say you can see about 3,000 stars in the dark countryside with the naked eye, but I'm sure there's much more. Don't even try actually to count the stars or you'll fall asleep and the show will be over!
In the dark countryside, you can't help but notice the bright band of milky light that bisects the sky from roughly north to south like a cosmic artist's stroke. You may have been taught at an early age that the band is the Milky Way galaxy.
While that's undoubtedly true, you must realize that every star you see anytime, including the sun, is a member of our home galaxy, the Milky Way.
Stars outside the band are relatively close by, and the stars in the band are much more distant and make up the plane of our home galaxy, the thickest part of the Milky Way. There are so many stars in the band that are so far away that we can all see a collective ghostly glow.
From all that's been learned over the last hundred years, astronomers have concluded that the Milky Way galaxy comprises about 300 to 400 billion stars forming a nearly circular disk broken up into spiral arms. There's a massive hump of stars in the center. The Milky Way is a little more than 100,000 light-years in diameter and 10,000 light-years thick, with one light-year equal to about six trillion miles. Our sun is about 30,000 light-years from the galaxy's center in one of the arms.
When you see that milky band, you’re looking along the thicker plane of our nearly circular galaxy. All of the stars we see obediently orbit around the center of the Milky Way, and our sun takes over 200 million years to make one circuit.
In case you're wondering, the center of the Milky Way lies in the direction of the constellation Sagittarius the Archer in the low southwest sky. Sagittarius's nickname is “the Teapot” because that's what it really looks like.
The Milky Way band is not all that much brighter around the teapot because there is a lot of dark interstellar gas and dust that block the “hump” at our galaxy's center. It's been said that if we could see the Milky Way's central region unobstructed, that area of the sky would be much brighter than a full moon!
Lie back on the ground or a reclining lawn chair and roll your eyes from one end of the Milky Way band to the other. A decent pair of binoculars will greatly enhance the celestial treasures you come across, like bright patches, dark rifts and star clusters. You'll probably even see a few human-made satellites rolling across the heavens.
While enjoying our galaxy, remember that our Milky Way is only one of millions of other galaxies out there. Astronomers have spotted billions and billions of galaxies more than 13 billion light-years away! It's a big sky out there for you to enjoy. Don't miss it!
Celestial Happening
Set your alarm super early this coming Friday night, Oct. 20, because the Orionid meteor shower is peaking early Saturday morning. The best time to see them will be around midnight to just before the start of morning twilight.
The Orionids are the most prolific meteor shower in October, and this should be a good year to see them because the moon will be out of the sky early Saturday morning, Oct. 21, making for a darker backdrop in the sky. You could easily see more than 20 meteors an hour or more in the countryside!
Mike Lynch is an amateur astronomer and retired broadcast meteorologist for WCCO Radio in Minneapolis/St. Paul. He is the author of “Stars: a Month by Month Tour of the Constellations,” published by Adventure Publications and available at bookstores and adventurepublications.net. Contact him at mikewlynch@comcast.net.
